Power shovel front end

ABSTRACT

A twin-section boom is pivotally attached to the front of an excavator frame, and a saddle block pivotally mounted approximately half-way up the length of the boom slidably retains a dipper handle that moves back and forth between the boom sections. A pinion gear located in the saddle block and driven by a hydraulic motor engages a rack gear on the underside of the handle to provide a crowd-retract motion. A dipper is rotatably attached at the forward end of the handle to prevent transmission of torsional forces along the handle, and the dipper is retained in an upright attitude by twin dual hoist ropes extending over boom point sheaves attached at the upper ends of the boom sections.

United States Patent Kraschnewski et al.

[ POWER Sl-IOVEL FRONT END [72] Inventors: Melvin W. Kraschnewski, Racine;

Gerald F. Lesniewski, South Mil- [451 Sept. 12, 1972 Primary Examiner-Philip Arnold Attorney-Arthur H. Seidel, Allan W. Leiser and John A. Thierry [57] ABSTRACT A twin-section boom is pivotally attached to the front of an excavator frame, and a saddle block pivotally mounted approximately half-way up the length of the boom slidably retains a dipper handle that moves back and forth between the boom sections. A pinion gear located in the saddle block and driven by a hydraulic motor engages a rack gear on the underside of the handle to provide a crowd-retract motion. A dipper is rotatably attached at the forward end of the handle to prevent transmission of torsional forces along the handie, and the dipper is retained in an upright attitude by twin dual hoist ropes extending over boom point sheaves attached at the upper ends of the boom sections.

2 Claims, 5 Drawing Figures whimznscmlm SHEET 1 OF 2 I7 [Ill INVENTORS MELVIN W. KRASCHNEWSKI GERALD F'. LESNIEWSKI ATTORNEY PATENTEDSEP 12 m2 SHEET 2 BF 2 INVENTORS MELVIN W. KRASCHNEWSKI GERALD F. LESNIEWSKI ATTORNEY POWER SHOVEL FRONT END BACKGROUND OF THE INVENTION The field of the invention is large power shovels of the type having a dipper on the forward end of a reciprocably mounted handle. The handle slides within a saddle block attached to the boom to provide a crowd-retract motion for the dipper, and ropes that extend over the end of the boom and then downward attach to the dipper to provide a hoist-lower motion.

During a normal operating cycle the dipper is crowded outward into a soil bank, hoisted upward to dig and fill the dipper, and then swung and dumped. To

reduce manufacturing costs, it is desirable to provide a shovel front end which is lightweight but can withstand the forces encountered during this operating cycle. Furthermore, lightweight construction of the front end minimizes its moment of inertia resulting in an increased swing speed. The forces acting on the shovel front end are greatest during the dig portion of the operating cycle. The hoist ropes absorb some of these forces, however, torsional forces which tend to rotate or twist the dipper during digging are transmitted along the handle and applied to the saddle block and crowdretract drive mechanism.

In'prior shovel front ends there are two basic means of attaching the handle to the boom to provide the crowd-retract motion and absorb the torsional forces applied to the'handle. A first method is the use of a rope-crowd mechanism as shown in U.S. Pat. No. 3,045,844 issued to Learmont et al. on July 24, 1962, in which the handle is both slidably and rotatably retained within the saddle block. A combination of ropes and pulleys are used to slide the handle within the saddle block to provide the crowd-retract motion. Rigid alignment of the rope and pulley arrangement is not required and the handle is allowed to rotate within the saddle block to prevent transmission of torsional forces from the handle to the saddle block and drive mechanism.

The second crowd-retract method used in prior shovel front ends includes a power-driven pinion on the boom in driving engagement with a gear rack on the handle, such as that disclosed in U.S. Pat. No. 1,698,421 issued to E. J. Wilson on Jan. 8, 1929. Rotation of the pinion slides the handle through the saddle block to provide a crowd-retract motion. To secure tight engagement between the gears, however, the handle must not rotate and as a consequence the torsional forces acting on the dipper are applied to the saddle block, drive mechanism and boom. The most practical method thus far developed for dealing with these forces is to use a double-handle for the dipper driven by two rack and pinion drive mechanisms attached on opposite sides of a one-part boom. Transversely spacing the rack and pinion gear mechanisms in this fashion provides a mechanical advantage, however, the necessary second handle and drive mechanism does add weight and increases the cost of the arrangement.

SUMMARY OF THE INVENTION The present invention provides a front end for a power shovel which includes a boom having a pair of spaced boom point sheaves, a saddle block attached to the boom intermediate its ends, a handle slidably mounted by the saddle block, a dipper rotatably attached to the end of the handle, and a rack and pinion drive mechanism-attached to slide the handle through the saddle block. The dipper is supported by at least two hoist ropes extending over the boom point sheaves and attached to the dipper on opposite sides of its axis of rotation.

It is a general objective of the invention to provide a power shovel front end which has a lightweight rack and pinion type crowd-retract drive mechanism which will withstand the torsional forces applied to the dipper during digging. This is accomplished by rotatably connecting the dipper to the handle. Torsional forces formerly transmitted to the rack and pinion drive mechanisms are absorbed by the twin hoist ropes connected to retain the dipper in its proper digging or upright attitude. This provides a substantial weight and cost reduction in the rack and pinion drive mechanism, handle, saddle block, and boom.

Another objective of the invention is to provide a power shovel front end having a rotatable dipper in which torsional forces are absorbed by the hoist ropes and wear of the hoist ropes caused by the resulting bending in them is minimized. By suspending the dipper from two transversely spaced hoist ropes attached to points on opposite sides of the dipper axis of rotation and passing them over spaced boom point sheaves, a mechanical advantage is obtained which translates the torsional forces to linear forces with minimal bending of the hoist ropes.

The foregoing and other objects and advantages of the invention will appear from the following description. In the description reference is made to the accompanying drawings which form apart hereof, and in which there is shown by way of illustration and not of limitation a preferred embodiment of the invention.

Such embodiment does not represent the full scope of the invention, but rather the invention may be employed in many different embodiments, and reference is made to the claims herein for interpreting the breadth ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view in elevation of a power shovel front end embodying the present invention,

FIG. 2 is a top view of a portion of the power shovel shown in FIG. 1,

FIG. 3 is a view in cross section of the power shovel front end of FIG. 1 taken on the plane 3-3,

F IG. 4 is a view in cross section with parts cut away of a rack and pinion mechanism taken on the plane 4- 4 ofFIG. 3, and

FIG. 5 is a partial top view with parts cut away of the rotatable connection of the dipper to the handle.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a standard power shovel has a frame 1 rotatably mounted on crawlers 2. The frame 1 supports the drive machinery, including a hoist drum 3, within a housing 4. The frame 1 also supports an A- frame structure 5, and a boom 6. The boom 6 is comprised of a left section 7 and a right section 8 each section having its lower end pivotally attached by means of pins 9 to the front of the shovel frame 1. Boom stays 10 are connected'to and extend from the apex of the A- frame to the upper end, or boom point, of each boom section 7 and 8. The boom stays l0 retain the boom 6 in an upright angle. Also, the use of two spaced boom stays l0 minimizes twisting forces applied to the boom 6 and pivot pins 9. The boom 6 is designed primarily to withstand compression forces, and the reduction of twisting and bending forces applied to it allows a substantial reduction in the weight and moment of inertia of the boom 6.

As shown in FIGS. 1 and 2, a shipper shaft 1 l is connected approximately half-way up the boom 6 through each boom section 7 and 8. As shown best in FIG. 3, the shipper shaft 11 is divided into two sections, each section securely attached to one of the two boom sections 7 and 8 and extending into the space between the boom sections. The shipper shaft 11 serves to rotatably suspend a saddle block l2 between the boom sections, on the ends of the shipper shaft 11 protruding inwardly from each boom section 7 and 8. The saddle block 12 has fore and aft guide sections 13 and 14 each with a rectangular handle opening. These openings are aligned to slidably receive a dipper handle 15 and retain it immediately above and in perpendicular orientation to the shipper shaft 1 1.

Referring to FIG. 3, a crowd-retract motion for the power shovel is provided by driving a pinion gear 16 located within the saddle block 12. The pinion gear 16 rotates about the central axis of the shipper shaft 11 and engages a gear rack 17 extending along the length of the underside of the handle 15. The pinion gear 16 is part of a drive shaft 18 which is rotatably retained within the saddle block 12 by means of two bearings 19 attached to the saddle block 12, one on each side of the pinion gear 16 along its axis of rotation. As shown in FIGS. 2 and 3, the drive shaft 18 extends inside the shipper shaft 11 through the left boom section 7 to engage a transmission-20 attached to the outer left side of the boom 6. The transmission 20 serves to match the speed and power requirements of the pinion gear 16 to the output characteristics of a hydraulic motor 21 mounted on the right boom section 8.

Rotatably connected to the operating end of the handle 15 is a dipper 22. The dipper 22 is of standard construction, having a door 23 on its underside operable to dump, or unload the dipper. The handle 15 has a light weight tubular construction with a generally rectangular cross section. A bearing ring 24 is firmly welded to the operating end of the handle 15 and a bearing pin 25 is securely attached to the bearing ring 24. The bearing pin 25 has a circular cross section with one end inserted in the handle 15 and the other inserted into a dipper collar 26 which rotates with the dipper 22 during digging. The collar 26 has two arms 27 and 28 extending out from each side and forward to pivotally attach to two ears 29 on the back of the dipper 22.

As shown in FIG. 5, the dipper 22 is retained on the bearing pin 25 by means of a thrust flange 30 formed on the forward end of the bearing pin 25. The thrust flange 30 is seated in an annular groove 31 at the forward end of the dipper collar 26 and bears against one side of this groove to retain the collar 26 on the bearing pin 25. A shield 32 is bolted over the open forward end of the collar 26 to prevent foreign substances from fouling the bearing surfaces inside and to retain the lubricant.

Referring to FIGS. 1 and 2, the rotatable dipper 22 is manipulated by means of a standard twin dual hoist rope arrangement. The rope arrangement is attached to the dipper 22 by means of a left lug 33 and a right lug 34 each formed on the top surface of the dipper 22, well spaced from each other on opposite sides of the dipper axis of rotation. A left equalizing sheave 35 is attached to a clevis 36 which in turn is pivotally attached to the left lug 33 by means of a pin 37. Likewise, a right equalizing sheave 38 is attached to a clevis 39 which is pivotally connected to the right lug 34 by means of a pin 40.

Connected at the top ends of the left and right boom sections 7 and 8 are left and right boom point sheaves 41 and 42. The boom point sheaves 41 and 42 are each dual sheaves of large diameter and are well spaced apart by virtue of their connection to the spaced boom sections 7 and 8. The boom pointsheaves 41 and 42 eliminate frictional wear of the hoist ropes 43 and 44 by providing a rotatable surface over which the ropes pass. The left hoist rope 43 is attached to the hoist drum 3, passes over the left boom point sheave 41, around the left equalizing sheave 35 on the dipper 22, back over the left boom point sheave 41, and back to the hoist drum 3. The right hoist rope 44 is strung in like manner; from the hoist drum 3, over the right boom point sheave 42, around the right equalizer sheave 38, back over the right boom point sheave 42, and back down to the hoist drum 3.

During typical operation, the power shovel may operate alongside a bank of ore or coal. The dig portion of the operating cycle is typically a coordinated hoist, crowd sweep of the dipper 22 upward through the bank. This upward sweep produces tremendous forces acting both linearly downward and torsionally about the dipper axis of rotation. The downward linear force is shared by the hoist ropes 43 and 44 and the handle, however, because of the rotational connection of the dipper, torsional forces are almost entirely absorbed by the hoist ropes 43 and 44. The use of spaced left and right hoist ropes attached to the dipper 22 outboard on opposite sides of its axis of rotation retains the dipper 22 in its upright, or digging, attitude despite uneven digging conditions tending to rotate it. The mechanical advantage obtained by the use of twin hoist ropes passing over spaced boom point sheaves minimizes bending of the ropes in reaction to the torsional forces applied to the dipper.

The rotational connection of the. dipper 22 to the handle 15 insures that no torsional forces are transmitted to the handle 15. This allows the use of a lightweight handle 15, saddle block 12, shipper shaft 11, and boom 6. These reductions in weight result in both a-cost reduction in the manufacture of the 2 a pair of spaced boom point sheaves each rotatably connected to the upper end of one of the boom sections;

a saddle block pivotally attached to the boom intermediate the ends of the boom;

a single handle slidably attached to the saddle block,

said handle having an operating end;

a dipper rotatably connected at the operating end of the handle for movement relative thereto;

a first hoist rope passed over one of said boom point sheaves and connected to said dipper outboard to one side of the dippers axis of rotation;

a second hoist rope passed over the other boom point sheave and attached to the dipper outboard on the 

1. A power shovel front end, the combination comprising: a boom extending outward from the power shovel, which boom includes a pair of spaced boom sections; a pair of spaced boom point sheaves each rotatably connected to the upper end of one of the boom sections; a saddle block pivotally attached to the boom intermediate the ends of the boom; a single handle slidably attached to the saddle block, said handle having an operating end; a dipper rotatably connected at the operating end of the handle for movement relative thereto; a first hoist rope passed over one of said boom point sheaves and connected to said dipper outboard to one side of the dipper''s axis of rotation; a second hoist rope passed over the other boom point sheave and attached to the dipper outboard on the other side of its axis of rotation; and drive means attached to move said handle with respect to said saddle block to provide a crowd-retract motion.
 2. The power shovel front end as recited in claim 1, wherein said drive means comprises: a gear rack attached to the handle; a drive shaft rotatably attached to said boom and including a pinion gear disposed between said boom sections and arranged to engage said gear rack and move said handle when the shaft is rotated; and means to rotate said drive shaft. 